Echo cancellers are well known in the art for providing cancellation of echoes resulting from imperfect impedance matching by hybrids in two-to-four wire signal conversion. Prior art adaptive linear echo cancellers (LECs) employing the Least Mean Square (LMS) algorithm are useful in quickly adapting to changes in the echo path response. However, such systems are computationally complex and slow in adapting to changes in the echo path or a sudden onset of echo during a call.
It is also known from the prior art to use complex and expensive echo locators for the purpose of determining echo delay and the dispersion time.
The following patents are exemplary of the prior art:    CA2319639 entitled Locating Network Echos, by Popovic et al, dated Mar. 14, 2000.    U.S. Pat. No. 5,721,782 entitled Partitioned Echo Canceller Utilizing Decimation Echo Location, by Piket et al, dated Feb. 24, 1998.    U.S. Pat. No. 5,761,638 entitled Telephone Network Apparatus and Method Using Echo Delay and Attenuation, by Knittle et al, dated Jun. 2, 1998.    U.S. Pat. No. 5,999,901 entitled Telephone Network Apparatus and Method Using Echo Delay and Attenuation, by Knittle et al, dated Dec. 7, 1999.    U.S. Pat. No. 5,511,064 entitled Speech Path Switching Control Apparatus and Method for Making Maintenance of Speech Possible Upon Occurrence of Fault in Echo Cancellation, by Oh et. al, dated Apr. 23, 1996.